I wouldn't think there would be a problem especially on a Monday. Most bothies empty after a Friday and Saturday night. Also, this bothy is a decent size, plenty of floor space even if you couldn't get onto one of the wooden platforms.
I stayed there in May on a Friday night and hubby and I had it to ourselves. The whole area is one huge building site at the moment,
I think it is a hydro scheme going in.
Hope you have a good walk.